The cranial placodes are transient embryonic structures that eventually develop into portions of the sense organs and the anterior pituitary, a major endocrine gland. These placodes arise from the ectoderm, one of the three germ layers, which is known to give rise to the epidermis, brain, and spinal cord. The placodes develop in a small region that is flanked by the developing brain and epidermis. Currently we understand very little of how these transient structures develop in humans. To gain better insight into this process, this project aims to determine the underlying molecular mechanisms that restrict the ectoderm to a non-neural fate and allow it to develop into the different placodes. Due to the early time points in which these tissues arise, development will be modeled using human embryonic stem cells. Stem cells will be subjected to different culture conditions to determine the optimal conditions to derive first non-neural ectoderm, followed by pre-placodal ectoderm and finally the different placodes. All of these tissues are defined by a distinct set of genes, which will be analyzed for co-expression at single cell resolution. This knowledge can be used to study how defects in genes alter placode development. As a step towards this, we will engineer an EYA1 knockout human embryonic stem cell line and assay changes in the transcriptional profile of these cells during placode development at single cell resolution. What we learn from this research has broad implications for study of human disease affecting the sensory organ systems, including the inner ear.